New foam with improved expansion behaviour when used in thin layers

Abstract

A thermally expandable composition, including (a) at least one polymer P, cross-linkable by a free-radical initiator, and (b) at least one solid butyl rubber BRu, and (c) at least one free-radical initiator, and (d) at least one blowing agent, and (e) at least one tackifier TA, whereby the cured expanded composition has a volume increase compared to the uncured composition of less than 1300%. The thermally expandable composition is able to provide good expansion behaviour and good adhesion on metal surfaces and is especially suitable for baffle and/or reinforcement elements, e.g. in automotive manufacturing.

1 . A thermally expandable composition, comprising
 (a) at least one polymer P, cross-linkable by a free-radical initiator, and   (b) at least one solid butyl rubber BRu, whereby the composition comprises the solid butyl rubber with an amount of between 5 wt.-% and 16 wt.-%, based on the total weight of the composition, and   (c) at least one free-radical initiator, and   (d) at least one blowing agent, and   (e) at least one tackifier TA,   whereby the cured expanded composition has a volume increase compared to the uncured composition of less than 1300%, whereby the volume increase is determined using the DIN EN ISO 1183 method of density measurement (Archimedes principle).   
     
     
         2 . The thermally expandable composition of  claim 1 , wherein the composition comprises the tackifier with an amount of between 12 wt.-% and 30 wt.-%, based on the total weight of the composition. 
     
     
         3 . The thermally expandable composition of  claim 1 , wherein the tackifier is a hydrocarbon resin. 
     
     
         4 . The thermally expandable composition of  claim 1 , wherein the composition further comprises at least one process oil PO selected from the group consisting of aromatic oil, naphthenic oil and poly(iso)butylene. 
     
     
         5 . The thermally expandable composition according to  claim 4 , wherein the composition comprises the process oil PO with an amount of between 18 wt.-% and 35 wt.-%, based on the total weight of the composition. 
     
     
         6 . The thermally expandable composition of  claim 1 , wherein the blowing agent is azodicarbonamide. 
     
     
         7 . The thermally expandable composition of  claim 1 , wherein the composition comprises the blowing agent with an amount of between 2.5 wt.-% and 6 wt.-%. 
     
     
         8 . The thermally expandable composition of  claim 1 , wherein the free-radical initiator is a peroxide or a perester. 
     
     
         9 . The thermally expandable composition of  claim 1 , wherein the composition further comprises at least one acrylate A. 
     
     
         10 . The thermally expandable composition of  claim 1 , wherein the at least one solid butyl rubber BRu is a halogenated butyl rubber. 
     
     
         11 . A baffle element for open or hollow structures, wherein the element comprises a thermally expandable composition according to  claim 1 . 
     
     
         12 . The baffle element of  claim 11 , wherein the thermally expandable composition has a sheet-like structure with a thickness of 0.5 to 10 mm. 
     
     
         13 . The baffle element of  claim 11 , wherein the thermally expandable composition has a sheet-like structure with a length of 5 to 30 cm. 
     
     
         14 . A method comprising using the baffle element of  claim 11  to seal or baffle a cavity or hollow or open structure of a land-, water-, or air-vehicle, and/or a cavity of a building such that the transmission of noise, vibrations, humidity, and/or heat is reduced. 
     
     
         15 . A method for sealing or baffling a cavity or hollow structure, wherein an element comprising a thermally expandable composition according to  claim 1  is introduced into said cavity or hollow structure and subsequently thermally expanded such that said cavity or hollow structure is at least partially filled by the expanded composition.